Desalination

ABSTRACT

IN A DESALINATION PLANT, SMALL QUANTITIES OF REFRIGERANT ARE STRIPPED FROM THE FRESH AND SALINE WATERS BY SUBJECTING THE WATER TO DIFFERENT DEGREES OF VACUUM AND THEN, PREFERABLY TO STREAM OF AIR.

NOV. 2, 197 1 MARTlNDALE El AL DESALINATION 9 sheets sheot 1 OriginalFiled Jan. 15, 1968 Om mm QB MAS Nov. 2, 1971 A. MARITINDALE L 3,616,612

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DESALINATION Original Filed Jan. 15, 1968 9 Sheets-Shee 4 NOV. 2, 1971MARTlNDALE ETAL 3,616,612

DESALINATION 9 SheetsSheet 5 Original Filed Jan. 15, 1968 FIG. 7

NOV. 2, 1971 MARTINDALE EI'AL 3,616,612v

DESALINATION QxigJlnal. Filed Jan. 15, 1968 9 Sheets-Sheet 6 NOV. 2,MARTlNDALE El'AL 3,616,612

DESALINATION Original F iled Jan. 15, 1968 9 Sheets-Sheet 7 PEG.

FIG. 9

DESALINATION 9 Sheets-Sheet 8 Original Filed Jan 15, 1968 0mm u momUnited States Patent US. Cl. 55-193 3 Claims ABSTRACT OF THE DISCLOSUREIn a desalination plant, small quantities of refrigerant are strippedfrom the fresh and saline waters by subjecting the water to differentdegrees of vacuum and then, preferably to stream of air.

This is a continuation of application Ser. No. 697,803,

filed J an. 15, 1968 and now abandoned.

This invention is concerned with improvements in or relating todesalination.

Shortage of fresh water is an increasing world problem and it has beenpreviously proposed to produce fresh water from, for example, sea water,by various methods of desalination. One previously proposed process ofdesalinating saline water to produce fresh water comprises the steps offreezing ice crystals out of the saline water, by boiling in the water avolatile liquid refrigerant immiscible with water, separating the icecrystals from their mother liquor, and melting the separated icecrystals; We mean this process when hereinafter we refer to a process ofthe kind referred to.

It is an object of the invention to provide an improved method ofdesalinating saline water.

It is another object of the invention to provide improved apparatusadapted for use in such a method.

Sea water usually contains between 32,000 and 38,000 parts per millionof dissolved salts and to render it fit for drinking purposes it is, forexample, desalinated to a salt concentration of less than 500 ppm,preferably less than 200 ppm, for other purposes however a higher saltconcentration may be acceptable.

According to one aspect of the invention, there is provided apparatusfor use in removing small quantities of refrigerant from water,comprising a container having a plurality of compartments in each ofwhich, in operation of the apparatus the water is subjected to a vacuumand means for providing different degrees of vacuum in each of thecompartments.

According to another aspect of the invention, there is provided a methodof removing small quantities of refrigerant from water wherein the wateris subjected to a plurality of different degrees of vacuum.

Additionally the water may be contacted with a stream of air.

Conveniently a desalination plant comprises apparatus in accordance withthe invention;

The invention also provides, in another of its aspects, fresh water whenproduced by a process as set out in the "ice last preceding paragraphbut one or the last preceding paragraph but three.

An embodiment of the invention in a desalination plant will now bedescribed, by way of example, with reference to the accompanyingdrawings, in which:

FIG. 1 shows a How diagram of the desalination plant, in accordance withthe invention;

FIG. 2 shows a sectional plan view of a freezer/crystalliser of theplant;

FIG. 3 shows a section on the line IIIIII of FIG. 2;

FIG. 4 shows a section on the line IV-IV of FIG. 2;

FIG. 5 shows a perspective view of parts of the freezer/ crystalliser;

FIG. 6 shows a sectional side view of a separator/melter of the plant;

FIG. 7 shows a section on the line VII-VII of FIG. 6-;

FIG. 8 shows a section on the line VIIIVIII of FIG. 6;

FIG. 9 shows a sectional side view of a butane condenser of the plant;

FIG. 10 shows a section on the line X-X of FIG. 9;

FIG. 11 shows a section on the line XIXI of FIG. 9;

FIG. 12 shows a section of the line XIIXII of FIG. 9;

FIG. 13 shows a sectional side elevation of a debutaniser of the plant;

FIG. 14 shows a section on the line XIV-XIV of FIG. 13. 1

FIG. 15 shows a section on the line XVXV of FIG. 13; and

FIG. 16 shows a section on the line XVIXVI of FIG. 13.

The desalination plant is adapted for use in desalinating sea water toproduce fresh Water by the steps of freezing ice crystals out of the seawater by boiling liquid butane in the water, separating the ice crystalsfrom their mother liquor, and melting the separated ice crystals toprovide the fresh water.

The plant (FIG. 1) comprises a freezer/crystalliser 12 adapted for usein producing ice crystals from sea water by direct contact refrigerationwith boiling butane, a separator/melter 14 arranged to separate the icecrystals from their mother liquor, to Wash adhering saline water fromthe ice crystals, and to melt the separated ice crystals.

The plant also comprises a sea Water intake unit 18, a strainer 16,indirect contact heat exchangers 20, 22, a butane condenser 24,debutanisers 26, 28, a reservoir 30, compressors 32, 34, and vacuumpumps 35, 37, 39; the strainer 16, the heat exchangers 20, 22, thecompressors 32, 34, and the pumps 35, 37, 39 are all of known type perse.

In the operation of the plant raw sea water is pumped continuously alonga line 36 to the intake unit 18 where it is coarsely screened to removelarge solid objects eg sea weed and fish. The sea water is pumped fromthe unit 18, along a line 38 which leads, via the strainer 16, to lines40, 42 leading to the heat exchangers 20, 22 respectively; in the heatexchanger 20 the sea water is cooled by indirect heat exchange withreject saline water from the separator/melter 14; in the heat exchanger22 the sea water is cooled by heat exchange with product water from theseparator/melter 14. The cooled sea water leaves the heat exchangers 20,22 by lines 44, 46, respectively which both lead into a line 48 leadinginto the freezer/crystalliser 12. In the freezer/crystalliser 12 icecrystals are formed and a slurry of ice crystals in saline water leavesthe freezer/crystalliser 12 along a line 50 which leads to theseparator/melter 14; in the freezer/ crystalliser 12 the saline water issuper-cooled by up to 0.3" F. Ice crystals separated in theseparator/melter 14 are melted therein by direct contact with butanevapour. The water melted from the ice crystals passes from theseparator/melter 14 along a line 56 which leads to the heat exchanger22. From the heat exchanger 22 the water passes along a line 58 to thebutane condenser 24.

The water then passes along a line 59 to the debutaniser 26 where smallquantities of suspended and dissolved butane are removed from the water.From the debutaniser 26 the water passes along a line 60 to thedebutaniser 28 where trace quantities of butane remaining in the waterare removed. The product fresh water passes along a line 62 from thedebutaniser 28 to the reservoir 30. Wash water for washing the icecrystals in H the separator/melter 14 is taken from the line 56 along aline 64.

The reject saline water from which ice crystals have been separatedpasses from the separator/melter 14 along a line 66 which leads to theheat exchanger 20. Saline water leaves the heat exchanger 20 along aline 68 which leads to the butane condenser 24; in the butane condenser24 butane vapour from the separator/melter is cooled and condensed byheat exchange with the saline water and with water from the heatexchanger 22; the saline water from the heat exchanger 20 and the waterfrom the heat exchanger 22 are kept separate in the butane condenser 24.The saline water leaves the butane condenser 24 along a line 70 whichleads to the debutaniser 26 which recovers small quantities of suspendedand dissolved butane from the saline water; in the debutaniser 26 thesaline water from the heat exchanger 20 is kept separate from the waterfrom the heat exchanger 22. The saline water is rejected from the plantalong a line 72 which leads from the debutaniser 26. Some saline Waterfrom the line 66 is recycled along a line 74 to the line 48 which leadsinto the freezer/crystalliser 12.

Butane for the freezing of ice crystals in the freezer/ crystalliser 12is pumped continuously round the plant in a closed cycle. Liquid butaneat a temperature not less than F. above that of the slurry in thefreezer/ crystalliser 12 enters the freezer/crystalliser 12 along a line96 and butane vapour leaves the freezer/crystalliser 12 along a line 78leading to the compressor 32. From the compressor 32 butane vapourpasses along a line 80 to the separator/melter 14 where it is cooled andpartially condensed by direct contact with the ice crystals, which aremelted. Liquid butane condensed in the separator/melter 14 leaves theseparator/melter 14 along the line 96 which leads to thefreezer/crystalliser 12. Butane vapour leaves the separator/melter 14along a line 82 which leads to the compressor 34. The vapour leaves thecompressor 34 along a line 84 which leads to the butane condenser 24where the butane is condensed by contacting reject saline water from theheat exchanger 22 and water from the heat exchanger from the butanecondenser 24 liquid butane is recycled to the freezer/crystalliser 12,for further boiling in saline water, along a line 76 which leads intothe line 96. Butane make-up enters the line 96 along a line 86 asrequired. The debutaniser 26 is operated at three different degrees ofvacuum which are maintained by the pumps 35, 37, 39. Butane vapourpasses from the debutaniser 26 along lines 88, 90, which lead, via thevacuum pumps 35, 37, respectively into a line 92 leading to the line 78which leads to the compressor 32.

As will be seen in FIG. 1, the vacuum pumps are arranged to apply thevacuum to the compartments on the fresh water side through the salinewater side of the container.

The intake unit 18 (FIG. 1) comprises a travelling band screen which iswashed by water recirculated from the line 38 via a pump 102. Solidmaterial screened by the screen 100 is rejected down a chute 104.

The freezer/crystalliser 12 (FIGS. 2-5) comprises a container for seawater in which are provided four bays 106, 108, 110, 112 which areseparated by a straight wall 114 and the limbs of a U-shaped wall 116;adjacent bays are connected by U-bends 118, 119, 121, 123; the bays106-112 provide a long extended flow path for water flowing through thecontainer 105. In the operation of the plant sea water enters the bay106 from the line 48 and follows a sepentine path through the bays 106,108, 110, 112, in the direction indicated by the arrows in FIG. 2.

The freezer/crystalliser 12 also comprises a weir plate 120 and someice/water slurry leaves the bay 112 ovet the weir plate 120 and passesvia a hood 122 into the line 50; the remainder of the slurry from thebay 112 is re-cycled to the bay 106 via the bend 123. The freezer/crystalliser 12 comprises two propellers 124 arranged to induce the flowin the direction of the arrows; each propeller 124 is located in one ofthe U-bends 118, 119. The weir plate 120 acts to disentrain butanebubbles from the slurry which is to pass over it.

The freezer/crystalliser 12 comprises a plurality Of horizontal pipes126 arranged for the injection of liquid butane for contacting withsaline water in the container 105; the pipes 126 are supported in thebays 106112 and in the U-bends 118123; there is a group of four pipeportions on either side of each bay 106-112; there is also a group offour pipe portions on either side of each U-bend 118121 and a group offour pipe portions on the inner side of the U-bend 123; in each of thetwo bends 118, 119 the pipe portions terminate clear of the propeller124. The pipes 126 are submerged in the operation of the plant and arespaced above a base wall 128 of the freezer/crystalliser 12. The pipes126 are connected to the butane inlet line 96 by a plurality ofdowncomers 130 and manifolds 132. Each pipe 126 is perforated with aplurality of evenly spaced small holes 127 (FIG. 5) which are providedalong the pipes 126 where they extend along the bays 106112 and thebends 118- 123; the pipes 126 are not perforated where they extendacross the bays 108112 at and across the bends 118, 119 at 127.

The freezer/crystalliser 12 comprises a plurality of vertical bafiles134 which are arranged on either side of each bay 106112 and each bend118-123. Each baffle 134 is submerged in the operation of the plant andis spaced above the base wall 128.

Each group of four pipe portions 126 is located between one of thebaffies 134 and an inner peripheral surface 136 of the appropriate bay106112 or U-bend 118123, the group of pipe portions being closely spacedto the baflie 134 and the surface 136; the lateral spacing between eachpair of adjacent baffles 134 is approximately the same as that betweeneach surface 136 and the adjacent bafiie 134 (FIG. 4). There arediscontinuities in the bafiies 134, extending past the inlet line 48,and in the bends 118, 119 the bafiles 134 terminating clear of thepropellers 124.

The butane outlet line 78 leads outwardly from an upwardly extendingportion 138 of the freezer/crystallizer 12; the weir plate 120 isdirectly below where the line 78 leads out of the portion 138.

In the operation of the plant, a slurry of ice crystals in saline waterflowing through the bays 106112 is kept continuously circulating aroundthe bafiies 134 in turbulent flow by the action of liquid butanecontinuously injected through the holes 127 for fiow up past the baffles134. The circulation takes place around the baffies 134 (FIG. 4) asfollows: up along the space between a baffle 134 and the adjacentsurface 136 and down along the other side of the baffie 134 and againinto the space between the baflle 134 and the surface 136 for flow uptherealong: this is indicated by arrows in FIG. 4. During circulationthe ice crystals are uniformly distributed in the slurry. Some brinefrom the line 48 is passed to sprays 139 arranged to keep roof supports137 of the freezer/ crystalliser 12 free of ice.

The separator/melter 14 (FIGS. 6, 7, and 8) comprises a circular tank140 in which are provided concentric outer and inner adjacent annularchambers 142, 144 respectively; both chambers 142, 144 are open at thetop.

In the operation of the plant ice crystals are washed and separated fromsaline water in the chamber 142; and in the chamber 144 ice crystalsfrom the chamber 142 are melted by contact with butane vapour, some ofwhich is condensed.

The chamber 142 is lined with a plastics liner 146 of, for example,polypropylene or polyvinyl chloride. A plurality of perforated draingrids 148 are provided in the liner 146 and are in communication withannular drainage boxes 150 which are connected by pipes 153 to theoutlet line 66. The separator/melter 14 also comprises an assembly 152which is mounted for rotation about the axis of the tank 140 and onwhich are mounted eight water spray tubes 154 and eight plough arms 156.

In the operation of the plant a bed of ice crystals and saline waterderived from the inlet line '0 rises slowly continuously up along thechamber 142 and saline water drains through the .grids 148, the drainageboxes 150 and the pipes 153 into the line 66. The plough arms 156continuously scrape ice crystals into the chamber 144 and wash waterfrom the line 64 is sprayed continuously onto the rising bed, at asufficient velocity to flood the bed, by the spray tubes 154; most ofthe wash water leaves the chamber 142 with the ice crystals entering thechamber 1 44 and only a little leaves with the reject saline water.

A wire mesh grid 158 extends across the chamber 144 and the ice crystalsfrom the chamber 142 are dumped onto the grid 158. Butane vapour fromthe inlet 80 enters an upper frusto-conical portion 160 of the tank 140n laminar flow and contacts the ice crystals on the grid 158. A plate159 extends across the chamber 144 below the grid 158 and four downcomerpipes 161 extend downwardly therefrom.

Water melted from the ice crystals and condensed butane pass downwardlythrough the pipes 161, collect in two layers below the plate 159 and aredrawn off from the separate layers to pass into the line 56, 96respectively.

The separator/melter 14 comprises an axial pipe 162 which leads to thebutane vapour outlet line 82; four p pes 164 lead from the chamber 144below the grid 158 into the pipe 162; uncondensed butane vapour passesfrom the separator/melter 14 to the line 82 via the pipes 164, 162. Theseparator/melter 14 also comprises an annular weir box 166 in thechamber 144 from which a pipe 168 leads to the liquid butane outlet line96 so that liquid butane collecting in the chamber 144 passes to theline 96. Water collecting in the chamber 144 passes to the line 56 bypipes 170 which lead from the bottom of the chamber 144.

The assembly 152 comprises a vertical shaft 172 which is mounted forrotation in the tank 140; in the operation of the plant the shaft 172 isdriven by an electric motor and gearbox unit 174. Four horizontal pipes176 extend radially from the shaft 172 and lead into a ring pipe 178.The spray tubes 154 are secured to the ring pipe 178 and the plough arms156 are also secured to the ring pipe 178 below the level of the spraytubes 154; the spray tubes 154 are in communication with the ring pipe1.78 and each tube 154 has a plough arm 156 adjacent thereto. Fourinclined pipes 184 extend from the shaft 172 to the pipes 176 and are incommunication with an annular box 186 which is secured to the pipes 184and with which the wash water line 64 communicates via downcomer pipes185. In the operation of the plant wash water is supplied to the spraytubes 154 from the line 64 via the box 186 and the pipes 184, 176, 178.Alternate plough arms 156 extend over the inner chamber 144 as well asover the chamber 142 while the remaining plough arms 156 terminatesubstantially at the inner periphery of the chamber 142.

The salt concentration of the water layer in the chamber 144 is measuredby an instrument (not shown) which controls the pressure at the drainageboxes 150. Variations in the salt concentration vary the suction on thedrainage grids 148 which results in variations in the amount of washwater being drawn through the ice bed.

The butane condenser 24 (FIGS. 9-12) comprises a tower 188 which isdivided into upper and lower compartments 190, 192, respectively, by abubble cap tray 204. Adjacent liquid spray devices 194, 196 are providedin the upper compartment 190; and adjacent packings 198, 200 of BerlSaddles are also provided directly below the spray devices 194, 196,respectively; the spray device 194 and the packing 198 are separatedfrom the spray device 196 and the packing 200 by a vertical partition202 which extends across the whole width of the tower 188. Adjacentpackings 206, 207 of Berl Saddles are also provided in the lowercompartment 192 directly below the packings 198, 200, respectively. Thepartition 202 also substantially separates the packings 206, 207 andsubstantially divides the bubble tray 204 into separate portions. Avertical tube .210 extends axially of the tower 188 from below thepackings 206, 207 to above the bubble t-ray 204; the tube 210 comprisesa conical lower outlet 212 and has a roof-shaped baflle 214 directlyabove its upper end. Bafiles 216, 218, 220, 222 are also provided in thecompartment 192 generally below the tube 210.

In the operation of the plant water from the line 58 if sprayed by thespray device 196 and saline water from the line 68 is sprayed by thespray device 194; in the tower 1 88 the water from the spray device 196is kept separate from the water from the spray device 194. Butane vapourfrom the line 84 enters the lower compartment 192 by inlets 224, 226 onopposite sides of the partition 202 respectively. The butane vapourentering by the inlet 224 passes downwardly through the packing 206where it is contacted in co-current flow with water, from the spray 194,which has passed through the packing 198 and been redistributed by thebubble cap tray 204 which acts to provide a liquid seal between thecompartments 190, 192; no gas passes upwardly through the tray 204. Somebutane condenses from the vapour and the remaining vapour passes up thetube 210 and into the packing 198 where it is contacted incountercurrent flow with water from the spray 194; this causes thebutane vapour to condense and it passes together with the water throughthe bubble cap tray 204 and the packing 206; the baffle 2-14 directsliquid away from the upper end of the tube 210. Butane vapour enteringthe inlet 226 is contacted with water from the spray device 196 in acorresponding manner. The liquid butane and water form two layers in thecompartment 192 on both sides of the partition 202 and liquid butaneleaves the tower 188 by outlets 228, 230 which both lead to the line 76.Saline water leaves the tower 188 by the line 70 and water from thespray device 196 leaves the tower 188 by the line 59. The batlies 216,218, 2-20, 222 act to provide seals around the outlets 228, 230, and thelines 70, 59.

The debutaniser 26 (FIGS. 13-16) comprises a tower 236 which is dividedinto upper, central and lower compartments 238, 240, 242, by liquid sealdevices 244, 246. Adjacent liquid spray devices 248, 250 are provided inthe upper compartment 238 and adjacent packings 252, 254 of Pall ringsare also provided directly below the spray devices 248, 250,respectively; the spray device 248 and the packing 252 are separatedfrom the spray device 250 and the packing 254 by a vertical partition256 which extends across the whole width of the tower 236. Adjacentpackings 258, 260 of Pall rings are also provided in the centralcompartment 240 directly below the packings 252, 254, respectively. Thepartition 256 also separates the packings 258, 260. Similarly, adjacentpackings 262, 264 of Pall rings are provided in the lower compartment242 directly below the packings 258, 260, respectively. Again thepartition 256 separates the packings 262, 264. Holes 265 are provided inthe partition 256 to equalise the gas pressures on either side thereof.Battles 266 are provided around the holes 265 to restrain passage ofwater there through. In the operation of the plant the threecompartments 238, 240, 242 are subjected to different degrees of vacuumby the vacuum pumps 35, 37, 39 respectively; the lowest degree of vacuumis in the compartment 238 and the highest in the compartment 242. Salinewater from the line 70 is sprayed by the spray device 248 and passessuccessively through the packing 252, the seal device 244, the packing258, the seal device 246 and the packing 262; the water leaves the tower236 by the line 72; water is re-distributed over the packings 258, 262by perforated plates 259, 261 of the seal devices 244, 246,respectively. Water from the line 59 is sprayed by the spray device 250,passes through the tower 236 in a corresponding manner and leaves thetower 236 by the line 60. Butane leaves the compartments 238, 240 by thelines 88, 90 which lead to the pumps 35, 37, respectively; butane leavesthe compartment 242 by a line 268 which leads via the pump 39 to thecompartment 240.

The debutaniser 28 (FIG. 1) comprises a tower 272 containing a spraydevice 274, a packing 275 of Pall rings and an air distributor 276 whichis supplied by a fan 278. In the operation of the plant water from theline 60 is sprayed by the spray device 274 and is stripped of butane onthe packing 275 by a countercurrent stream of air from the airdistributor 276. The air containing the stripped butane enters theatmosphere via a chimney 280.

In modified forms of the plant one or more of the followingmodifications are made:

(a) Each heat exchanger 20, 22 is replaced by a double direct contactheat exchanger employing an intermediate heat exchange medium.

(b) A sieve bend classifier of the kind referred to in UK. patentspecification No. 791,520 (Stamicarbon) is inserted in the line 50following the freezer/crystalliser 12. In this case crystals below acertain size are returned to the freezer/crystalliser 12 to form newcentres for crystal growth or to be destroyed with consequentabstraction of their latent heat of fusion from the incoming salinewater.

(c) The sea water feed is de-aerated.

Typical operating conditions for the plant in a temperate climate are asfollows:

Mass flows (lbs/hr.)

Sea water feed: 5.2 million. Product desalinatcd water: 2.1 million.

Recycle reject saline water to freezer/crystalliser: 3.5 million.

Recycle reject saline water to freeze/crystalliser: 3.5 million.

Ice in ice/water slurry out of freezer/crystalliser: 2.2

million.

Saline Water in ice/water slurry out of freezer/crystalliser: 6.6million.

Liquid butane from separator/melting to freezer/crystalliser: 1.9million.

Liquid butane from butane condenser to freezer/crystalliser: 0.3million.

Gaseous butane into separator/melter: 2.2 million.

Retention time in freezer/crystalliser: 7 minutes.

Linear velocity in freezer/crystalliser: feet/second.

Wash water leaving separator/melter with reject brine: 5% of productwater.

8 Temperatures F.)

Heat exchanger 28:

Sea water feed in: 50 Sea water out: 34 Reject saline Water in: 26Reject saline water out: 43 Heat exchanger 22:

Sea water feed in: 50 Sea water out: 38 Product water in: 32 Productwater out: 43 Freezer/crystalliser 12:

Feed in (including saline water recycle): 31 Slurry out (and incontainer 105): 26 Liquid butane in: 35 Butane vapour out: 24Separator/melter 14:

Slurry in: 26 Slurry from chamber 142 to chamber 144: 32 Product waterout: 32 Reject saline water out: 26 Butane vapour in: 37 Butane liquidout: 35 Butane vapour out: 35 Butane condenser 24:

Product water in: 43 Product water out: 54 Saline water in: 43 Salinewater out: 54 Butane vapour in: 55 Butane liquid out: 55 Vacuumdebutaniser 26:

Operating temperature: 54 Air stripper debutaniser 28:

Operating temperature: 54 Salt concentrations (parts per million):

Sea water feed: 35,000 Product desalinated water: Pressures (lbs. persquare inch absolute):

Freezer/crystalliser: 12.6 Separator/melter: 15.9 Butane condenser: 23.8Vacuum debutaniser: 3.74; 1.11; and 0.33 Air stripper debutaniser:atmospheric. Ice crystals:

Etfective diameter: 0.5 mm. (Carman-Kozeny) Thickness: diameterPercentage solids in freezer/crystalliser: 25%

Butane n-Butane with a boiling range extending over not more than 18F.and with not more than 1% impurities having a Henrys law constantgreater than that of n-butane.

Concentration in saline water entering vacuum debutaniser: 100 ppm.

Concentration in product water entering vacuum debutaniser: 200 ppm.

Concentration in each water stream leaving vacuum debutaniser: 2 ppm.

Concentration in product water stream leaving air stripper debutaniser:0.2 ppm.

We claim:

1. Apparatus for use in removing small quantities of refrigerant fromsaline water and fresh water in a desalination process, comprising acontainer, a vertical partition dividing said container so as toaccommodate separate flow paths of saline water and fresh water down thecontainer, said partition having apertures therein to allowintermingling of the refrigerant vapor removed from the respectivewaters, bafiie means for restraining passage of the respective watersthrough the apertures, means dividing the container transversely so asto provide a plurality of compartments for each of the water flow paths,and means for applying a differ- 10 ent degree of vacuum to eachcompartment of the re- 2,834,466 5/1958 Hament 55-196 X spective flow p2,904,511 9/1959 Donath 6258 X 2. Apparatus as claimed in claim 1,wherein the vacu- 3 220 203 11/1965 Rose 62 58 um applying means isarranged to apply the vacuum to the compartments on the fresh water sidethrough the 5 36240324 3/1966 Ashley et 6258 saline water side of thecontainer. 3,250,081 5/1966 Othmer 6258 3. Apparatus as claimed in claim1, wherein the vacuum applying means is arranged to feed from the OTHERREFERENCES compartments havillg the highest degree of Vacuum into JohnW. Pike, The Direct Controlled Crystal Desalia compartment havlng alower degree of vacuum. 10 nation p Oct. 39, 19 PP- 2 and The ReferencesCited First International Symposium on Water Desalination.

UNITED STATES PATENTS REUBEN FRIEDMAN, Primary Examiner 2,085,028 6/1937Kelley 55196 X 2,420,356 5/1947 compa 15 R. W. BURK Assistant Ex mm r

